Tag: hvac

This is the second article in a three-part series, where Advanced Psychrometrics are explored. The source material for each of the articles in this series is ACCA Manual P Sections 3, 4, and 5. This article is based on information found in Section 4.

If you followed the previous Advanced Psychrometrics article, you now know how to use a Psych Chart to plot a Room Sensible Heat Ratio (RSHR) Line, and how to calculate Design Room CFM. However, if you followed that exercise, you will note the absence of real-world variables, such as ventilation and bypass factors. Equipment Sensible Heat Ratios are almost never an exact match to the RSHR. This exercise will account for these variables, and walk you through how to plot these properties on a Psychrometric Chart.

It is worth reminding you that this is an exercise to help illustrate the complexities of psychrometry in the real world. This may not always be a practical method utilized in the design process.

When outdoor ventilation air is mixed with return air before the equipment coil, the equipment is exposed to latent and sensible loads beyond that of just the conditioned space. This characteristic causes the Coil Sensible Heat Ratio (CSHR) to alter from the RSHR. Remember, the Room Design Conditions will be met only when the supply air properties fall on the RSHR Line. With two different SHRs, we no longer have the luxury of choosing any supply condition we wish. The supply air must be able to cool and dehumidify the space. It also must now compensate for the additional load introduced by the ventilation air. Therefore, the only supply condition that will satisfy the Room Design Condition is the point at which both the RSHR Line and CSHR Line meet on the Psych Chart.

To plot the RSHR Line should be a breeze at this point. For a review on that process, and the first part of this article series, CLICK HERE.

The construction of the CSHR Line, however, is a bit more involved. There is a little trial and error in the construction of the CSHR Line. It’s not impossible, of course, and with practice, you get pretty good at nailing it on the first try. Here’s why a trial and error process is required in order to plot the CSHR Line:

The location of the CSHR Line is determined by the Mixed Air Condition (MAT) and CSHR

The CSHR and the MAT can’t be plotted without knowing the percentage of Outdoor Air (OA)

The percentage of OA can be calculated only when the supply CFM is known.

The supply CFM can be calculated only when the ΔT between the room return and supply is known, which is determined by the intersection of the CSHR and RSHR Lines

The CSHR Line is the line we are solving for; therefore, it is unavailable.

This is why a trial and error process is required. Simply put, we’re going to use an estimated guess as to what we think our supply air condition will be, then follow the process until we can determine if our selection actually results in the intersection of the CSHR and RSHR Lines. To help aid in the accuracy of your guess, keep in mind that, on average, a Direct Exchange Fan Coil can provide supply air temperatures which may fall between 14-25 degrees below the space temperature at typical relative humidities between 80% and 95%.

To begin this exercise, let’s start with some basic information, which will ALWAYS be available to you from a quality load calculation. This information can be plotted on the Psych Chart with complete certainty:

Room Sensible Heat: 21,700 BTUh

Room Latent Heat: 2,300 BTUh

Room Total Heat: 24,000 BTUh

RSHR: 0.90

Room Design Condition: 75℉ db / 50% RH

Outdoor Design Condition: 95℉ db / 75℉ wb

Ventilation Required: 245 CFM

In this scenario, a Room-to-Room load calculation has been done on a home. The RSHRs have all been averaged together for a mean room sensible heat ratio. We can go ahead and plot what we can on the chart:

Let’s select a 57℉ supply temperature at about 90% RH. Now we can determine the Supply CFM. Since the RSHR is the average of the entire home, the Supply CFM will equal the total system CFM.

CFM = Room Sensible Load ÷ (1.08 x ΔT)

21,700 ÷ (1.08 x 18) = 1,116 CFM

Now that we know the Supply CFM, we can calculate the percentage of ventilation air.

Ventilation = 245 CFM ÷ 1,116 CFM

Ventilation = 22%

We have a good bit of information here now, but the math starts to get a little confusing without explanation. We now know that 22% of Outdoor Air (at 95℉ db / 75℉ wb) will be mixing with the remaining 78% Return Air (at 75℉ db / 50% RH). To calculate the Mixed Air Condition, complete the following equation:

MAT = (0.22 x 95℉) + (0.78 x 75℉)

MAT = 20.9℉ + 58.5℉

MAT = 79.4℉

We can now plot the Mixed Air Condition on the Psych Chart.

At this point, we have everything we need to construct the Coil Sensible Heat Ratio Line. If you notice on the Psych Chart, there is a list of helpful formulas to the left of the page. We need to solve for Total Coil Heat Load (Qt) if we are to determine Coil Sensible Heat Load (Qs) and CSHR. To do that, we need to figure out the change in enthalpy (ΔH). Enthalpy is heat energy in BTUs per pound of dry air.

ΔH = 30.6 – 23.4

ΔH = 7.2

Now let’s plug our ΔH into the Total Coil Heat Load calculation. (4.5 here is Air Density x Run Time in minutes. 0.075 x 60 = 4.5)

Qt = 4.5 x CFM x ΔH

Qt = 4.5 x 1,116 x 7.2

Qt = 36,158 BTUh

Solve for Coil Sensible Heat Load. To do this, make sure you are using the entering air condition the equipment will actually see: MAT.

Qs = 1.08 x CFM x ΔT

Qs = 1.08 x 1,116 x 22.5

Qs = 27,119 BTUh

We can finally solve for Coil Sensible Heat Ratio at this point:

CSHR = Coil Sensible Load ÷ Total Coil Load

CSHR = 27,119 BTUh ÷ 36,158 BTUh

CSHR = 0.75

We can now plot the CSHR Line on the Psych Chart.

If you look closely, you may be thinking, “Wait a second, the CSHR Line does not intersect with the RSHR Line.” You would be absolutely correct. This is why the trial and error solution is necessary. However, if you notice, the CSHR Line is extremely close to our selected supply temperature. The CSHR Line is just slightly above the RSHR Line.

What does this mean?

We can still use the design CFM and supply condition, and the equipment will satisfy the sensible load, but will maintain a slightly higher humidity level in the space than what was designed. Take a look at the actual grains of moisture for the Mixed Air Condition in comparison to the Supply Air off the coil at 57℉.

The equipment will be able to dehumidify from 73 grains of moisture/lb of dry air down to 63 grains of moisture, rather than the ideal 62 grains. We’re talking about a difference of 1 grain of moisture. This can be acceptable, and the difference likely unnoticeable. In cases where a coil selection will not match the latent load requirements of a space, a viable option would be to add supplemental dehumidification to deal with the remaining latent load. Ultra-Aire Ventilating Dehumidifiers are an excellent option, and will also help lessen the additional latent load from the ventilation air.

Lastly, let’s talk about Bypass Factor. Remember, the ideal supply temperature would be the apparatus (equipment) dew point. However, there is a small percentage of air that will bypass the coil and not transfer its heat to the coil. This can be calculated using the known apparatus dew point. The Bypass Factor formula is as follows:

At this point, you would need to look up a manufacturer’s extended performance data for their equipment to ensure that the coil you select will meet a sensible capacity of 27,119 BTUh and a total capacity of 36,158 BTUh at 1,116 CFM, with an entering condition of 79.4℉ db / 65.6℉ wb and an outdoor condition of 95℉ db / 75℉ wb. Let me translate that to something you might actually see on a Performance Table:

Entering Air Condition: 80℉ db / 67℉ wb

Outdoor Air Conditions: 95℉ / 75℉ wb

Total Capacity: 36,000 BTUh

Sensible Capacity: 27,000 BTUh

Airflow: 1,100 CFM

If you can select a coil that will match these criteria, you will be able to maintain an indoor air condition that is nominally close to your design.

To see how this chart would look in another scenario (without going through the step-by-step process), here is a psych chart based on my house and ASHRAE Design Conditions:

Room Sensible Heat: 16,800 BTUh

Room Latent Heat: 7,200 BTUh

Room Total Heat: 24,000 BTUh

RSHR: 0.70

Room Design Conditions: 75℉ db / 50% RH

Outdoor Design Conditions: 90℉ db / 80℉ wb

Ventilation Requirement: 46 CFM

In this case, my selected supply air condition happened to fall perfectly at the intersection of the CSHR and RSHR Lines. The tricky part, however, is finding a coil that will meet the sensible and latent heat requirements under the design conditions. I would need to look for a coil with 18,000 BTUh sensible capacity and 29,000 BTUh total capacity. I’d have to settle for a 2.5 ton (30,000 BTUh) coil with a close CSHR under design conditions, and potentially add supplemental dehumidification. (A Carrier FB4C–030 would actually fit the bill quite nicely.) Remember, the equipment selection performance table will have actual capacities that differ from the nominal rating; thus, care must be taken when using manufacturer performance tables to select equipment.

If you’ve made it to the end of this exercise, congratulations: you are as nerdy as they come! I hope this helps illustrate the complexities of psychrometrics. If nothing else, the take away should be a new-found respect for psychrometrics, and its integration into a technician’s daily diagnostic toolbag.

Stay tuned for Part 3, where we will dive into ACCA Manual P, Section 5. There we will learn how to account for duct gains, and how reheat dehumidification looks on a Psych Chart.

This is the first of a three-part series of articles, which will dive deep into Advanced Psychrometrics. The source material for each of these articles may be found in ACCA Manual P Sections 3, 4, and 5. This article is based on information found in Section 3.

Psychrometrics is the study of the physical and thermodynamic properties of gas-vapor mixtures. In HVAC/R, we are specifically interested in air-moisture mixtures, and how varying properties affect human comfort and equipment performance. The Psychrometric Chart is a tool used to describe all the possible combinations of gas-vapor mixtures, and can be used to calculate the sensible and latent loads associated with HVAC/R equipment.

Using a Psychrometric Chart can be a bit confusing at first, but with practice and familiarity of the formulas, a Psych Chart can be easily used for a wide variety of purposes. Basic Psychrometric education can be found in the Refrigeration and Air Conditioning Technologies Manual (RACT) and in the first two sections of ACCA Manual P. In this article, however, I’m going to show you how you can apply psychrometrics to calculating Design Room CFM and illustrate how psychrometry can be used to help a technician understand supply air properties. All of the information discussed here can be found in Section 3 of ACCA Manual P.

When selecting equipment for a home or building, it is recommended a Room-to-Room Heat Load Calculation be done as opposed to a Block Load Calculation (Wrightsoftis an excellent software for load calculations, just saying). Room-to-Room calculations result in a more accurate representation of the heat gains and losses per zone (room), and can greatly improve the accuracy and performance of system sizing and design. Assuming a Room-to-Room Load Calculation has been done on a building, the next step in utilizing the Psychrometric Chart would be to plot out the Room Sensible Heat Ratio Lines for each zone. Room Sensible Heat Ratio (RSHR) is the ratio of sensible heat to total heat (including latent) for a room (or zone). If, for example, a room had a total heat load of 2,500 BTUh and 1,800 BTUh sensible heat, the RSHR would be 0.72.

RSHR = Room Sensible Load ÷ Room Total Load

RSHR = 1,800 BTUh ÷ 2,500 BTUh

RSHR = 0.72

Now that we know the RSHR, it’s time to plot the RSHR Line on the Psych Chart. To do this, we need to find a “reference dot”.

80℉ db at 50% RH is considered the standard reference dot. Locate and mark the reference dot and then run a line through the reference dot using a straight edge that is lined up with the RSHR (0.72), which can be found on the far right-hand side of the chart.

Now, locate the design conditions for the zone in question. Let’s say the design conditions (on a design day of 90℉) is 75℉ db at 50% RH. Plot that dot on the chart. Now, run a line straight through that dot heading to the left of the chart, making sure it is parallel to the reference line. This line is your RSHR Line. This line may now be used to select a supply air condition that will maintain the design room condition on a design day. However, the supply air condition must fall somewhere between the design room condition and dew point (which in this example is about 51.5℉). Theoretically, the lowest possible supply air condition would involve the evaporator coil in cool mode to be 51.5℉ (dew point), and the supply air leaving the register to be the same. However, this theory is in no way practical when you consider duct gains, air leakage, and bypass factors (let alone the fact no one wants a sweaty supply register). Practically, a supply condition falling somewhere between 80%-95% RH will result in good dehumidification, lower airflow, and low fan power consumption.

Select a supply temperature condition. For this example, let’s choose 55℉ at 90% RH. The next step is to calculate the Design Room CFM. The equation for CFM is as follows:

CFM = Room Sensible Load ÷ (1.08 x ΔT)

Remember, the Sensible Load for this zone is 1,800 BTUh. The difference between the Room Condition and the Supply Air Condition is 20℉.

CFM = 1,800 BTUh ÷ (1.08 x 20℉)

CFM = 83

The required volume of air given an hour of the runtime is 83 CFM for this room to maintain the design room air condition under design load.

But what if my ΔT is lower?

The required volume of air increases. The new supply air condition is 63℉ at 72% RH, giving us a ΔT of 12℉.

CFM = 1,800BTUh ÷ (1.08 x 12℉)

CFM = 139

Both of the different supply air selections will maintain the design room condition on a design day, because they each fall on the RSHR Line. But as the temperature difference between return and supply air decreases, the required CFM increases.

Some caveats must be addressed regarding this formula, and I credit Alex Meaney with Wrightsoft and Genry Garcia with Comfort Dynamics, Inc. for helping me understand these complexities. Both gentlemen are brilliant-minded experts in their fields, and have contributed (and continue to contribute) to HVAC School.

First, the runtime is specified in minutes, because we are solving for cubic feet per minute (CFM), but also using British Thermal Units per hour. Converting the hour of runtime to minutes gives us 60 minutes, and makes sure our units of measurement are compatible.

Second, you may notice the term isobaric. This refers to any property at a constant pressure. At sea level, atmospheric pressure is around 14.7 psia. At this presumed fixed pressure, the density of dry air is 0.075 lb/ft3, and the specific heat of dry air is 0.24 BTU/lb/℉.

In reality, atmospheric pressure is not fixed, and outdoor air is not always dry. While you may be able to correct for actual pressure and humidity, it may not always be practical. On the other hand, with the ability to use MeasureQuick (which corrects for air density and pressure in its calculations), the processes discussed in these articles may become more practical. It is important to note that manufacturers use isobaric air density and specific heat in their capacity ratings and airflow calculations. Therefore, the argument could also be made that even with this caveat, the end result will (on average) still land you nominally close to the actual air condition requirements.(Please note the wording used here) 😉

So how does this all circle back to practical application? It must be understood that a coil can operate in only one sensible heat ratio at a time, and it may not equate to any of the RSHRs calculated for any particular zone. In the case of a home with multiple zones, you may choose one of the following options when selecting a cooling coil to match the load conditions:

If humidity control is critical to a specific zone, use the RSHR for that room to select a coil. All other rooms will vary in humidity, but the critical zone will be maintained.

Average all the RSHRs together for a mean RSHR that can be used to select a coil. Each room will vary slightly from its individual RSHR, but it will be minimal and likely unnoticeable.

And that, in a nutshell, is how you may use a Psychrometric Chart and data from a Load Calculation to determine Room Design CFM. This exercise, however, merely scratches the surface of the many factors that must be considered in an HVAC system. This exercise works only for a system that does not suffer from duct leakage, bypass factor, and has no ventilation whatsoever for the home/building. This exercise would fall short of providing any real-world insight into psychrometric properties involving an HVAC system. However, the skills learned here translate into the next phase of advanced psychrometrics! In the next two articles, I will detail how these variables can be accounted for (even solved for). In the end, I hope you will understand a little more about Psychrometrics in general, and how to add that knowledge to your ability to efficiently diagnose a system as a whole (including the envelope and people).

I’ll end this article with a quote from Alex Meaney, and I think it is important to keep this idea in mind throughout the rest of this series of articles:

“I’m of the opinion that local humidity is usually a[n] infiltration/ventilation/return problem, not a supply problem.”

–Alex Meaney

For access to the Testo Psych Chart I used for this article, click here.

Many installers and service technicians know how to read and use a manufacturer fan table, but this is a quick review with a few extra tips for newer techs. It’s also a good reminder to senior technicians how this easy-to-use practice can also be easily abused.

At installation, it is imperative to the performance and longevity of the appliance to set up airflow properly. A practical way to do this is utilizing the manufacturer-supplied fan tables found in every installation manual. Here’s a review on how to set up airflow on a new system:

Determine your target airflow (The national average is 400cfm/ton. However, in a dry climate, design airflow may be 450-500cfm/ton, and in a humid climate, airflow is typically designed at 350-300cfm/ton.)

Set your fan speed (choose the speed tap, or set the dip switches)

Verify the equipment and duct work is clean, and all packing materials are removed from inside the appliance (yes, this gets missed sometimes)

Run the system in order to achieve the test conditions in which the Fan Table was created (Fan Table airflow readings are only valid if the field conditions match as closely to the lab conditions as possible; i.e. wet coil, dry coil, with or without heat strip kits, etc.)

On the fan table, find the model matching the equipment you have, and locate the speed tap being used

Match the real-time static pressure with the fan table

The point at which both the TESP column and Speed Tap row meet is the corresponding estimated airflow.

Make any adjustments to ductwork or fan speed in order to achieve the target airflow (This is made easy if ductwork is slightly oversized and installed with manual dampers on the supply.)

TruTechTools.com

For servicing, techs may use the fan table method as a quick and dirty way of verifying airflow without extensive and time-consuming testing. This can be acceptable, but only if the following conditions are met:

The equipment and ductwork are clean (This includes making sure the filter has been replaced)

The equipment has been benchmarked once before (Without a reference, the fan table cannot be relied upon as an accurate representation of estimated airflow.)

The equipment is running as closely to the documented lab conditions as possible. (But even then, how wet is “wet”?)

Static pressure readings stand alone as a valuable measurement during a service call, and TESP can inform a technician whether more extensive testing is required. But if the equipment has never been worked on by you, or your company did not install the equipment, the fan tables will not be useful until a full-system commissioning has been completed.

Carrier FB4CNF Installation Manual

Another important tip is to always keep the return static pressure below 0.4” w.c. According to many manufacturers’ literature, a return static pressure of 0.4’ w.c. or higher can potentially result in water from the primary drain pan being picked up and thrown around inside the cabinet area, and sometimes into the ductwork.

It is important to understand static pressure measurement is NOT a measurement of airflow. This is where many technicians abuse this method. Static pressure is just that: a measurement of pressure in reference to the space outside the ductwork. Based on lab testing conditions, a manufacturer is able to determine the airflow of a system under a known resistance. Static pressure is used as a proxy to estimate airflow, but this method is only as good as the conditions in which it is applied. Static pressure readings are air density dependent, so zeroing a manometer in a cold, dry attic, then inserting the probes into a humidified, warm duct system will adversely affect the accuracy of your measurements. This method is also heavily dependent on how detailed the manufacturer fan table is. An example of a good fan table would be one that lists the equipment model, if the unit was tested under wet or dry conditions, if heat strips were installed during testing, and any corresponding wattage/rpm determinations under given conditions.

Carrier FB4CNF Installation Manual

The difficulty with using Fan Tables as a way to measure airflow is realizing the resistance across the equipment is dynamic, and will likely change many times over the course of a test (the coil may get wetter as it is loaded with latent heat, the coil will become dirty over time, etc.) Measuring actual airflow is difficult to do, but static pressure measurements are still very valuable, and are a good way to determine if a problem exists and on which side of the ductwork it exists (supply or return).

A great product for measuring airflow in the field is the TrueFlow Grid by The Energy Conservatory. For more information on Airflow and Airflow Measurements, TruTechTools has an entire section of literature and webinars on the topic. Here is a video we recorded for them in 2017 regarding Static Pressure and Fan Tables:

Newer technicians often get hung up and frustrated when searching for low voltage shorts. This is understandable due to the broad spectrum of possibilities for the location of the short. However, this doesn’t mean the process needs to be complex. The time it takes to find a low voltage short may vary greatly depending on where the short is located, what components are failed, and how tedious the equipment is to access. Regardless of these variables, there are a few common processes that can make the technician’s life a bit easier when diagnosing a low voltage short. [Quick note: this is a guide for diagnosing a dead short in the low voltage circuit. In other words, the fuse immediately blows upon return of power to the appliance]

The first step is ALWAYS a visual inspection. You can save a lot of time and frustration by simply using good observation skills. Look for rub outs, loose connections at switches and coils, discoloration, wire splices, splits in wire insulation, etc. These can all give a technician a great starting point to searching for a short of any kind. I’ve done many visual inspections and found other issues unrelated to the short that may have gone unnoticed without thorough observation. This is why good observation skills and a thorough visual inspection is a great tool to use no matter what you’re diagnosing.

The second recommended step would be to power down the appliance and install a resettable fuse. You can find this valuable tool for cheap at any supply house, or you could even make your own from an old transformer that utilized a resettable fuse. This prevents a technician from blowing through 20 fuses before the source of the problem is found. Be careful the resettable fuse product you choose, some of them don’t trip as quickly as the factory and we have seen transformers and boards fail due to this. We suggest going to a 3A version rather than 5A when possible for additional protection.

Step three: Rule out the transformer and thermostat. These components are rarely ever the issue, but the thermostat is also one of the first things newer techs will replace when panicked and trying to solve a low voltage problem. The first quick tests will help rule them out entirely. With your meter, check primary and secondary voltage against the rated voltage on the transformer. If the transformer secondary voltage is 24v, it is typical to see a range between 22v-28v. If you measure higher or lower than normal voltage from the transformer, it may be a good idea to disconnect the transformer from the circuit and ohm out the windings and check for low resistance, which would result in higher amperage.

Remove the thermostat from the wall, and unwire all the wires except Common. Then, using either a pair of jumpers or a wire nut, connect R, G, Y, O, W wires together. Now, re-energize the system. If the fuse pops, the thermostat is NOT the problem, because it isn’t even in the circuit and the fuse still popped. If the fuse holds, and the equipment is running perfectly fine without the thermostat in place, then you may start to suspect the thermostat.

Next, remove the jumpers or wire nut and isolate R, G, Y, O, W wires from each other. Reset the fuse, and one by one jump G, Y, O, W to R. Eventually, one of those combinations will pop the fuse, and it will be in that circuit the short is located. For example, let’s say the Y wire circuit pops the fuse when jumped to R.

At this point, you’ve isolated the problem circuit, and you can begin testing everything related to that circuit. On a split system, the Y wire circuit will have the wire run from the thermostat to the indoor unit, from the indoor unit to the outdoor unit, from the outdoor unit to any defrost boards and switches, from those components to the compressor contactor. The best way to determine what is in the circuit is to read a wiring diagram, then follow the wire to verify the schematic. It is at this step a technician will repeat the visual inspection; this time more focused on a specific circuit.

If your testing leads you to suspect the wiring itself, you may isolate the wire by disconnecting the low voltage wire from the Outdoor unit completely. If the fuse still trips without any appliance connected to it (except the transformer power), then you can be certain the short is in the wire harness.

The final step in the process is to make all necessary repairs. Don’t forget to remove your resettable fuse and install a new, appropriately sized fused for the appliance! This process is one of MANY processes senior technicians have developed, and you may find yourself using your mentor’s methods, instead, and that’s perfectly fine. Just remember to always diagnose the WHOLE system! Never know what else might be happening once the short is repaired, and you can operate the system again.

For another take on a low voltage short diagnostic that comes with a little entertainment, here’s #BERTLIFE Ep. 4

I was pretty new in business and my first real “employee” hire in the HVAC part of Kalos was my brother Nathan, who many of you know as he is quite famous or infamous in the social media circles (which it is, is for you to interpret).

We won a custom new construction home job as the HVAC contractor and this was a “custom” job to be sure. I think it may have been the first house this builder had ever built and he planned almost nothing.

I remember walking the job with him after the slab had been poured and asking, “Did the plumber run chase lines for the copper?” as it was clearly supposed to have been based on the layout, and he looks at me like I have three heads and one of them is on fire and says “What’s that?”.

We agreed that we would run line covers on the outside even though I hated to do it on a nice new house. The day arrived to run the copper and I started laying it out. The builder took one look at the covers and grunts “you aren’t putting those on the wall, those are hideous”, which they were of course (this was before the paintable plastic covers we use today). So we start walking all around the house looking for some way to pack out a wall on this concrete block house so we could punch out four line sets from the inside.

We finally settled on a spot and I started running line sets. I asked Nathan to punch through the holes in the block so we could run the lines (Yes, I would do this all very differently today so don’t ask all the obvious questions), he walks off and I don’t think much more about it.

Fifteen minutes later I round the corner to check his progress and I see him, bent over, smacking the concrete block as hard as he could with a CRESCENT WRENCH.

It’s been about twelve years since that job and a lot has changed for the better, Nathan is still the sort of guy who is more prone to use the tool in his hand rather than buy something flashy but he’s actually an incredible tech and has harnessed much of that early lack of preparedness into practical resourcefulness.

Resourcefulness and Preparedness

Accountants are prepared, they need to know every rule and have all of their I’s dotted and T’s crossed. If you throw a complicated problem at a good accountant they are prepared to take care of it with precision and if they have any questions they will make 100% sure they get them answered 100% correctly and precisely before they proceed. It’s important that they are that way to keep us out of trouble with the IRS.

HVAC techs aren’t accountants

We can prepare as best we can and sometimes something goes wrong, the valves at the rack doesn’t hold, the aluminum coil has a leak, the product is going to spoil and the Shizzle is about to hit the Fizzle.

This is why techs need to be both prepared with the proper tools, resources, materials, confidence and know-how to jump in and IMPROVISE.

Some techs use resourcefulness and improvisation as an excuse not to be prepared and others blame less than ideal circumstances when things go arwy to explain away their failure to execute.

You don’t need to choose… go ahead and do both, be both prepared and resourceful, do things by the book when you can and absolutely improvise when you must.

Practice in our field isn’t like practicing the piano for a concert. For us it’s more about learning while doing and redoing and redoing and improving every time we do rather than repeating the same mistakes and preparation errors over and over.

Deep Understanding

In our trade there are two levels of thinking, the first is always looking for what “works” and ways to get by. An example is a residential installer who knows to connect R to Red, C to Blue, G to Green and so on. He knows that when he does that and flips the breaker…. most of the time IT WORKS! He also knows about this thing called a meter, he has one in his bag and sometimes his boss tells him to poke it around in the unit a bit to “measure” some things called voltage and amperage and write the stuff that shows on the screen down on paper.

I know I sound condescending but if you are, or have been in the field you know I’m not exaggerating at all. This installer knows what works (most of the time) and he stops there. As far as he is concerned his bag is full of all the tools he needs because at the end of the day the unit usually blows cold (or hot).

We have all been there and maybe are there at one aspect of the business or another because we are just trying to scrape through a tough day without having our ignorance revealed (it’s how I feel every time I have Bergmann on the podcast).

But listen up for a second….

STOP THAT

You never need to stop filling your skills and knowledge tool bag. NEVER!

If you haven’t tried brazing aluminum or steel before… give it a shot

Does rack refrigeration intimidate you? Look for an opportunity to work on it a bit.

You don’t learn well from reading? Guess who else didn’t… Hellen Keller, because she was BLIND and DEAF and she ended up becoming one of America’s most well known authors.

If you are good at your job and make a good living doing this stuff, CONGRATS, but that doesn’t mean you should stop growing and start allowing your brain to skills to decline.

If you are bored start doing new things like –

Measuring Airflow (for real, not just checking static)

Do a duct design (the right way)

Learn more about VRF, COw, Hydrocarbons, PVE oil etc…

Start flowing nitrogen while brazing and using a micron gauge (seriously stop making excuses about that)

Get better at combustion analysis

And the list goes on and on…

Keep adding tools to your skills toolbox, it will make your work more enjoyable, you will be more equipped to help others and you will increase your earning potential AND your ability to fix those really tough issues that has everyone else scratching their heads.

Those are the moments a good tech smiles… steps on his metaphorical (or literal) cigarette butt and digs deep into his bag of tricks… a bag that keeps growing every day.

We can all agree that the future we all would have expected for 2020 when we rang in the new year isn’t the one we got. We are all worried and looking to hedge our bets or cut our losses in one way or another and that makes sense. Given what we now know let’s take a look at a brighter future and imagine what that might look like if we start making moves toward it.

Interest In “Essential” Jobs

I understand that for the moment during “stay at home” even our industry is seeing layoffs, but for us that won’t last long.

The reality is that once this all settles down there will be a lot of people who want to work in jobs that aren’t as impacted by economic swings. While there will still be a huge shortage of skilled workers in the trade we will have an opportunity to bring in some new people to the trade who will value the piece of mind it can bring.

Rise of Practical Product Performance Testing

When we have big problems people tend to come together to find real, practical solutions. I hope to see more of this lead to better testing standards for IAQ products so that we can compare them head to head and make the best choices.

In this test of a DIY filter from Smart Air Filters, they show the DATA of how well a DIY filter can do in reducing very small particles from indoor air. In our podcast with Founder Thomas Talhelm, we talk about how getting better data and interpreting it in clear and honest ways may be the future of the IAQ industry and that’s a future I can get behind.

Apprenticeship Revolution

Registered apprenticeship programs are a really nice alternative to college where students can learn as they are employed with participating employers. Many people will have a desire to get out of debt and stay out debt while they pay their bills from their own efforts. I look forward to the future where more companies participate and more high-quality techs spend time teaching in the field and in classroom settings.

Cut Through Red Tape

We’ve already seen many building departments going to remote video inspections and many previously “essential” processes going to the side to keep the world running. While some of this isn’t always the best, I hope some of the best parts remain and video inspection seems like a really good idea to save time and labor and dare I say pollution? (less driving around and return trips).

More Technology Solutions

How many people have and will use ZOOM for meetings, online learning for classes and online signature capture for forms and documents? Necessity is forcing us to adapt and learn new things. Even NATE and RSES are embracing online accredited classes and remote proctoring for exams which will be HUGE in helping busy people.

Disruptive Innovation

When the going get’s tough we often rethink the way things are done. I talked with Michael Housh and Jim Bergmann about some of the problems we could solve with a self-contained, R-290 heat recovery chiller in residences. Far fetched? maybe… but big ideas can lead to practical steps of growth and that always excites me.

Return to Fundamental Business

What are some good fundamentals to follow? You already know them but let’s do this anyway.

Don’t go into debt

Only spend money you have

Make due with what you have and save your money to grow

Hire good people and train them for the skills

Fire people who don’t do their job well or exhibit toxic behaviors and do itquickly

But if we have learned anything we have learned over and over that steps towards progress have setbacks and unexpected discoveries that can sometimes lead to greater progress than we could have expected.

At the time of the publication of this article, COVID-19 (coronavirus) is spreading across the world at an alarming rate, and many people have self-quarantined to help slow and/or stop the spread of the virus. These precautionary measures are prudent and responsible. However, with the increased amount of time people will now spend inside their homes, there is a hidden factor to be aware of, which many people won’t think about. The prolonged occupancy of homes with increased cooking, bathing, and cleaning time will significantly impact the indoor air/environmental quality of these homes. An issue like this may not be measurable, but it is inevitable. In a time when many technicians, companies, and manufacturers will use this health crisis as a way to promote the sale of IAQ products in ways that can only be judged as unethical, it is imperative to the honest and curious technician to understand how to do her part in educating customers, and keeping everyone healthy.

This article will stay away from talking about specific types of boxed devices out there that “purify” the air, because that’s a topic for another day. The focus here is on the three main processes available to technicians and homeowners to improve indoor environmental conditions. Taking these one by one, technicians should have a thorough crash-course understanding of each and its importance to indoor air quality (IAQ). Ventilation, Filtration, and Humidity Control.

The first step in understanding a healthy indoor environment is to recognize the villains one must fight against in order to keep an environment healthy. Particulate Matter (PM), Volatile Organic Compounds (VOCs), Humidity (high or low), Carbon Monoxide (CO), Carbon Dioxide (CO2), Ozone (O3), etc. are just a few. These are the elements that tend to concentrate themselves in tight indoor environments. Each of the “Holy Trinity of IAQ” is designed to deal with these undesirables in their own dedicated way.

Everyone should know what a bath fan is. If you don’t have a bath fan, you probably live in a house not updated since the 1970s, and you likely have other decor issues to deal with as well. Bath fans are the most common mechanical ventilation in homes today. They are a form of negative pressure ventilation. As the fan pulls air from the room and expels it (hopefully not in your attic), this creates a negative pressure on the building envelope, and air from outside is pulled in through the cracks and crevices around your windows, door frames, attics, and through Jerry’s mouse hole…which everyone has…right? This type of ventilation is by far one of the least desirable, because you exact zero control over the quality of air you are bringing into the home. The air could be high in humidity and temperature, or it could be passing through layers of blown-in insulation inside your attic; neither of which are ideal. Air from these places isn’t really fresh.

The general consensus is that positive or balanced pressure ventilation is best. Examples of positive pressure ventilation include Make-up air units (MAU), Dedicated Outdoor Air Systems (DOAS), and the use of a scuttle (a small duct run from outdoor air into the return ductwork for HVAC systems). Balanced pressure ventilation is accomplished through mechanical equipment like Energy Recovery Ventilators (ERV), Heat Recovery Ventilators (HRV), and Conditioning Energy Recovery Ventilators (CERV). Each of these technologies has their advantages and ideal applications. The reason positive/balanced ventilation is desirable is for its ability to control the fresh air. If you can control the air you breathe, you can keep it “fresh”. For all of these options, there are applications for which they can be used that actually improve upon the quality of the air entering the space. But why do we care about ventilation? What’s so important about it?

Houses used to be built loosely. This isn’t to say they were built poorly, but houses used to be loose enough to allow for tons of natural ventilation. The codes and standards have evolved, and we now construct assemblies more airtight than in the past. This is why the EPA has published that indoor environments are often 2-5 times higher concentrations of air pollutants than outdoor levels, and can reach upwards of 100 times worse! This is because as people bathe, clean, and cook, VOC concentrations, Particulate matter, and humidity levels increase dramatically. People thought bath fans were for bathroom odors, but really that’s just a nice side-effect. They are for removing water vapor during and after showers/baths. Ventilation is utilized to dilute VOCs, CO, CO2, and other chemicals in order to maintain a comfortable indoor environment. I know of people who grew up watching their mother open all the windows of the house for a couple hours a week in order to “flush” the house. Mechanical ventilation is just like that, except more controllable and technologically advanced.

Particulate Matter is another indoor environment characteristic, which can cause a variety of health concerns. Particulate matter is categorized by its size in diameter, which is measured in micrometers (or microns). A lot of buzz is generated around PM 2.5, which is particulate matter with a diameter of 2 and a half microns; that is due to PM 2.5’s ability to do major damage to the human respiratory system. To give you an idea of the size of PM 2.5, the EPA has published that PM 10 is considered inhalable. PM 2.5 is 75% smaller than that! This means PM 2.5 tends to stay in the air stream longer than larger, denser particles. However, PM 2.5 is not the smallest particulate matter that can potentially do harm. PM 1 and 0.5 are also in the air, and they can easily make their way to our lungs and bloodstream. In order to combat against these airborne particles, it is important to filter the air with a high-quality air filter. There are filters designed to trap PM 2.5 and smaller (MERV 11 up to HEPA), and they are a critical component to any air distribution system. The third edition (2018) of the EPA Technical Summary of Residential Air Cleaners states that a MERV 13 is recommended for every HVAC system, or as high a MERV rating as the system will allow.

It is important to note that Particulate Matter does not refer to just dust. Particulate matter can be made up of pollen, viruses, bacteria, fibers, fungal spores, vehicle exhaust, etc. This fact makes it clear that filtration is not only important for the HVAC system, but also for the incoming air to any mechanical ventilation system. Humans are constantly submerged in this fluid called air. We must give more thought to the quality of the air we breathe.

The final head of our three-headed IAQ dragon is Humidity Control. This can refer to either high or low humidity levels. Either extreme is unhealthy and can create an environment prime for health risks. On one hand, high humidity can cause respiratory issues, encourage dust mite life, allow viruses and bacteria to increase, allow VOCs to become airborne, allow increased chemical reactions, and allow microbiological growth to take place. On the other hand, low humidity levels can also cause respiratory issues, irritate mucous membranes, allow viruses and bacteria to increase, and allow for the production of ozone. The happy medium is the generally accepted ideal humidity index, which falls between 35%-60% relative humidity.

In order to control humidity indoors, a technician must be aware of her climate zone, and whether she must work to increase or decrease humidity levels indoors in relation to outside levels. For arid climates, humidification is necessary, and options such as higher airflows and in-duct steam humidifiers are great solutions. For humid climates, running lower airflows and adding mechanical supplemental dehumidification is ideal. Some dehumidification systems allow for ventilation as an option, and they include a high MERV filter to cover all the bases. This option is an ideal solution for certain applications. Humidity must be controlled in an occupied space for that space to be comfortable. People are much more sensitive to humidity than temperature.

Looking at these three paths to creating and maintaining healthy air inside a home, it is important to realize these are Indoor Air Quality solutions. To create and maintain a fully comfortable indoor environment, air leaks, insulation, and load matching are other issues that would need to be addressed. However, in addressing the current issues with air quality in homes, this “Holy Trinity” is all any technician needs to exert energy into in order to help keep occupant air clean. There is a mindset that humans are never more intimate with their surroundings than when they inhale the air into their bodies. Technicians must take action to educate consumers and recommend the most effective solutions for IAQ improvement.

There are many companies and manufacturers using this health crisis to promote the sales of popular air “purifiers”, which use chemistry to “clean” the air in lieu of ventilation, humidity control, and filtration. The technology of these products will be discussed in a later article, but the most important take-away at this juncture is how important it is to maintain control over the humidity, the outdoor air coming into the space, and the concentration of particulate matter in the air stream. The methods of dealing with the issues mentioned in this article are the only methods that have been time and volume tested over decades, and they have standards in place to help ensure their effectiveness on IAQ.

So what do technicians do right now? Many homeowners may not want to spend the money on advanced in-duct filtration, mechanical ventilation, and humidity control during this time of uncertainty. Joe Medosch from HaywardScore.com has shared a very ingenuitive and affordable solution for many people to effectively filter indoor air.

This DIY method is a great way to help encourage homeowners to remain healthy as they spend more time inside their homes. This “box fan filter” may also make it more viable for sensitive people to open their windows and doors for longer periods of time during pollen season, as this enhances the circulation of air inside, and adds filtration throughout the home. Another recommendation for homeowners is to utilize the bath fans and kitchen exhausts as a way of ventilation. ALWAYS run a bath fan during bathing activity, and continue to run it 10-15 minutes afterward in order to prevent as much water vapor as possible from remaining inside the home. Portable dehumidifiers and humidifiers are also available.

Another recommendation for every technician, business, and the homeowner is the use of IAQ monitors throughout the home. Real-time monitoring and translation of data over time allows people to see the effects of their activities on IAQ. For technicians and businesses, it is a great way to track the effectiveness of your work over time. Without measurements and testing, you can only guess!

As we work together to combat the spread of viruses in our communities and around the world, the HVAC/R industry has a large opportunity to help educate customers on how to create and maintain a healthy indoor environment. We must take care to avoid fear-mongering and sales tactics geared toward the exploitation of people’s vulnerability and miseducation. Practice integrity, do your research, and implement industry best practices always.

This is the tale of how I found myself stuck on a service call for over 12 hours on a weekend, due to my failure to re-diagnose an issue. I was working for a service company that had many accounts with local gas stations. These were large customers, and we did everything we could to keep them happy.

One Friday as I was gearing up for my on-call weekend, I was informed I must travel an hour and a half away early the next morning to a gas station where another technician had diagnosed a faulty X-13 blower motor. The technician didn’t have the right blower motor for the repair, so the system was still down. The catch was: no one knew what size blower motor was supposed to go in. No model numbers, no detailed notes, nothing. So I grab every size aftermarket X-13 motor I could find in the shop. I had up to ¾ HP.

I arrived to find this location had two 5-ton package units mounted atop stands lifted 8 feet off the ground. After I setup the ladder and double-check the motor size, I realized it was 1 HP. I began calling all the parts houses in the area, hoping someone answered on a Saturday morning at 8am. No luck. I called parts houses in my local area and my co-workers to try and find a 1 HP X-13 motor that would work. Finally, I got in touch with one of my local suppliers. He had a motor that would fit the system I was working on, but he was an hour away from the supply house, and I was an additional hour and half away. Luckily, my employer at the time picked it up for me, and I had the part within a couple hours. I still had not re-diagnosed the system at that time.

Once I had the motor in hand, I quickly replaced it and had everything back together in a snap. I re-energize the system and….I curse loudly. The motor wouldn’t run. NOW I start re-diagnosing, a step I should have taken when I first arrived. Turns out, the original motor was just fine. The motor was not receiving 24v to the motor module, due to a faulty fan relay. I swapped out the 90-340 relay in the electrical compartment, restarted the system, and the blower ran beautifully. I hated myself.

I entertained the idea of packing up, walking away, and calling it complete, but I knew too well how that plays out. I began running complete system diagnostics, and found the system charge to be very low. I started leak searching the system with Big BlueⓇ from Refrigeration Technologies, and discovered a micro leak on the mechanical connection between the distributor tube and the TXV. No rubs outs were apparent, and it wasn’t a super loose connection, but it was clearly leaking. This was a package unit, remember, so I had to recover the entire system charge before I could make any repairs.

Once recovered, I found the connection was just coming loose. A healthy dab of NylogⓇ on the fitting connection and a torque wrench was all I needed to pass a nitrogen pressure test. Of course, the repair process was time-consuming, but eventually, I had the system evacuated, cleaned, recharged, and operating in peak condition under the current load.

I still would have needed to make the leak repair no matter what, but I could have easily saved 3.5 hours of time if i had re-diagnosed the system first when I arrived to the job. One could argue I was simply distracted by the chaos of the call, which would be true. However, a good technician should be able to follow the proper processes in spite of disorganization and frustration. I learned the importance of always checking behind yourself and others when you arrive to make a repair. Since, I have found the real causes for issues that were previously (either by me, or another technician) diagnosed as bad TXVs, reversing valves, motors, etc.

ALWAYS double-check your work and other people’s work. You never know how valuable it is until you fail to do it, and it costs you time and money.

Everyone in the HVAC/R trade uses some form of torch to braze or solder alloys together. So what is the proper way to handle an oxyacetylene torch? Turns out, there’s more than one right answer. Depending on which torch rig you use, the manufacturer’s manuals for operation may vary.

Everyone (hopefully) knows a neutral flame on a torch tip is suitable for most applications. Sometimes a carburizing flame is useful for reducing oxidation. The only flame we all should avoid is the oxidizing flame. However, in order to achieve the correct flame, a technician must fully understand the type of torch tip they are using, and the application for which the torch is being used.

For example, a “rosebud” tip is a (often) a large high BTU tip, and may be too large for most residential applications. A lot of technicians will attempt to lower the fuel and oxygen pressures feeding the tip to reduce the temperature. However, the tip begins to starve due to a lack of adequate fuel/oxygen mixing, and the flame will back into the torch tip and coat the inside with a carbon coating, which can damage the tip and torch over time. On the other hand, a torch that is too small will never get hot enough for an application outside its design parameters.

So what tips are best? At what pressures must tips be set? There are many answers to these questions, and they all depend on the brand of equipment you use, and the application in which you work.

I had the opportunity to speak to Tim Thibodeaux from the Service Dept. at Victor Technologies, and with Matt Foster from Uniweld Products, Inc. Both confirmed that pressures are tip specific, and operating procedures are brand-dependent. For example, many technicians have been taught to shut off the FUEL first when shutting down the torch, but this contradicts manufacturer instructions.

Uniweld states in their operation manual to shut off the OXYGEN first at the torch when following proper shutdown procedures. This is done to prevent flashback, or backfire.

Uniweld Shut-down Prodedure

Victor Shut-Down Procedure

Victor, too, requires the operator to shut off the OXYGEN first at the tip, then the operator may shut off the fuel valve. The reasoning remains the same: to prevent backfire/flashback. So where does this “Shut off the fuel first” myth come from? Turns out, it’s been taught that way for decades, but not without reason.

I had the opportunity to speak with HVAC/R Training Legend Bill Johnson, one of the original authors of the Refrigeration and Air Conditioning Technologies (RACT) Manual, and we spoke extensively on the topic. The RACT Manual offers an alternative method of shutting down the torch rig. The textbook teaches to shut the FUEL off at the torch first.

“Shut off the fuel gas (acetylene) valve at the torch first”Refrigeration and Air Conditioning Technologies (8th Edition)

I asked Bill Johnson why that was, and he explained it was a way of protecting the technician over the tool. Starve the flame of its fuel first, and eliminate the flame right away. Also, this was the way he had been taught many years ago, and the first edition of the RACT Manual was published in 1987. Perhaps there was once a manufacturer operation manual that specified the “fuel off first ” method, but the procedures have since changed. This method is not without merit, as its intentions are pure.

With the proper PPE and setup procedures, following the manufacturers’ approved operation instructions should be standard across the trade. Some would argue that shutting the oxygen off first can cause the little carbon “bunnies” that are created when the acetylene pressure is low enough. This is easily rectified by changing the way you setup the torch to begin with keeping acetylene pressure at the tip specified level.

Uniweld Tip 17-1

Matt Foster from Uniweld mentioned several operating tips for torch tips and setting a flame. The most common torch tip he finds most technicians use is the Type 17-1, and is good for pipes with an inside diameter of up to 1”. The manufacturer’s design operating pressures for this tip is 5 acetylene/5 oxygen. Another common tip is the Rosebud Type 28-2; its operating pressures are 5-7acetylene/5-8 oxygen, and it is good for pipes with an inside diameter of up to 1-5/8”. (Caveat: According to Matt, these published operating pressures may be even higher, as torch tip engineering changes over time, and the current catalog has not yet been updated. Therefore, when in doubt, take a look at the spec sheet that comes with the torch tip, or call the manufacturer to clear things up).

The Uniweld welding/brazing tip rated operating pressures can be found in their catalog here. The Victor welding/brazing tip rated operating pressure can be found here. As you can see, there is no one right answer when it comes to setting regulator pressure at the tanks. In schools, it is often taught to set fuel to 5psig at the regulator, and oxy at 10psig at the regulator. Some say the pressures should be the same at the regulator. The purpose for the pressure specifications is to ensure proper mixing of the gasses for the best quality flame, and to protect the torch rig from damage and compromised safety functions. So the answer to how to set your oxyacetylene regulator pressures is: it depends!

In other words…RTFM! (Read the FANTASTIC Manual) Hopefully, this clears up any confusion about torch rig operation and setup/shutdown procedures. Remember to ALWAYS wear proper PPE when dealing with any flame (eye protection, gloves, etc, and avoid polyester clothing), and follow industry best practices regarding safety.

Pump down solenoid valves are commonplace for any refrigeration technician. They are energized with the compressor still running, shutting off flow in the liquid line so the refrigerant is pumped into the condenser and receiver. The compressor will then shut off once a low-pressure switch opens the circuit when the pressure falls below a set pressure. However, there are other applications for which liquid line solenoid valves are useful. Long line applications in HVAC incur a wide range of challenges a technician must evaluate. Among those challenges include oil return, refrigerant migration in off-cycle, compressor workload, efficiency and capacity losses, added refrigerant charge, and metering device selection.

Long line applications (for R410a straight AC and Heat Pumps with ⅜” liquid lines) are generally defined as any system with a line set longer than 80 ft in equivalent length. Equivalent length in this context means that all pressure drops (copper fittings, bends, diameter size changes) translate to a length equivalent to a run of straight copper. Manufacturer spec data for copper fittings will have printed the equivalent length of those fittings in its literature. The length to be exceeded before long line application procedures are used may vary depending on line set diameter size and on which plane the indoor and outdoor units are located, but 80 ft is the general rule for Residential AC and HPs. Any system with a 20 ft uninterrupted vertical rise in the line set should also be treated as a long line application, per Carrier’s Long Line Application Guideline, which will be linked here.

There are many ways manufacturers have sought to resolve the challenges with long line applications. Some of these solutions include crankcase heaters and txv metering devices. Most manufacturers will specify an OEM hard-start kit for the purposes of protecting compressor effectiveness against the added refrigerant charge. Some commercial applications require oil traps to aid in oil return.

Liquid line solenoid valves are specifically utilized to prevent refrigerant migration in the off-cycle. The valve is positioned with the arrow printed on the valve body pointing toward the outdoor unit. For heat pumps, the valve must be biflow. It is important to note that the valve is normally closed in these long line applications. When energized with the contactor of the outdoor unit, the coil in the valve body will pull the valve open to allow flow. However, when closed, the valve only stops refrigerant from flowing in the direction of the arrow printed on the valve. With the system in the off-cycle, the solenoid valve will keep refrigerant liquid and vapor from migrating to the compressor down the liquid line. But don’t let the refrigerant tubing size fool you! Just because the liquid line is 3/8″ doesn’t mean any liquid line solenoid valve with 3/8″ sweat or flare connections will do. Care must be taken when selecting a solenoid valve. Choose valves to match the capacity of the system on which it will be installed (with a pressure drop of no more than 1 psi), then pay attention to refrigerant rating, THEN select by line set diameter size.

Wiring a liquid line solenoid valve will generally tap in with the thermostat’s call for the compressor. The valve should be wired into the Y (outdoor unit contactor) and C (common) terminals on single-stage equipment. For two-stage equipment, make sure the valve opens with a call for the first stage of heating or cooling (Y1). This prevents the valve from remaining closed during compressor operation.

Solenoid valves are incredibly simple in design and operation, and troubleshooting for long line applications is also quite simple. Confirm the coil is receiving its rated applied voltage when the system is energized, and test temperature drop across the valve. A maximum of 3° difference is allowable. The valves are NC (normally closed), so if there is a temp drop across the valve body, but no applied voltage during system operation, confirm your wiring.

Always make sure you are applying industry best practices when installing a solenoid valve. Remove the coil from the valve body before installation to prevent overheating. Use a heat absorption putty, spray, or wet rag on the valve body. Flow nitrogen while brazing, and install filter driers everytime (oversized if possible).

Long-line applications are few and far between in residential HVAC. But if you ever encounter a situation where you see a liquid line solenoid valve next to the outdoor unit, pay close attention to the way that system is setup and any other added accessories that may have been installed. You may refer to the Residential Long-Line Application Guideline at any time.

Refrigeration Technologies

VENOM PACK CONDENSER
PURE CONCENTRATE COIL CLEANER
Venom Pack Condenser Cleaner is a high foaming pure concentrate liquid designed to tackle the toughest soils. The proprietary blend of specialty detergents will liquify heavily embedded grease and grime to restore heat transfer and increase the efficiency of the coil.

Viper Condensate Pan and Drain Treatment is a sprayable gel. It coats the pan, p-trap and drain piping with a lubricative film to improve flow and prevent future soil adhesion. The slow dissolving enzyme gel will outperform and outlast conventional tablets and strips.

One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.